The present invention relates to an apparatus for controlling a ventilation fan, which automatically carries out ventilation in offices, living rooms, kitchens, etc. depending upon an environmental change.
As highly airtight designs for recent residence houses and offices have been advanced, ventilation fans have become more widespread. Automatic ventilating apparatus for automatically carrying out the ventilation depending upon the environmental change have been demanded.
Such a prior art apparatus for controlling a ventilation fan is generally formed as is disclosed in Japanese Unexamined Patent Publication No. Sho 62-59319. The structure of the prior art apparatus will be described with reference to FIG. 5.
The apparatus for controlling a ventilation fan comprises a sensor circuit 101 for detecting an environmental change (for example, pollution of indoor air) to generate a d.c. voltage, a reference voltage generating circuit 102 for changing a reference voltage with the lapse of time by capacitors and a resistor and the like, a comparing, operating and amplifying circuit 103 and a determining circuit 104 as shown in the drawing.
The operation of the thus formed apparatus for controlling the ventilation fan will now be described with reference to FIGS. 5 and 6.
Pollution of indoor air is detected by the sensor circuit 101, which feeds to the comparing, operating and amplifying circuit 103 a d.c. signal voltage D depending upon the level of pollution of the air. The comparing, operating and amplifying circuit 103 compares the signal voltage D with a reference voltage E which is generated by the reference voltage generating circuit 102. The determining circuit 104 detects a change in the signal voltage D from the sensor circuit 101 (Fa or Fb) based upon a result of comparison and a voltage instruction which has been fed to the reference voltage generating circuit 102 for operating the ventilation fan.